1. Field of the Invention
The present invention relates to shift control methods/systems for at least partially automated vehicular mechanical transmission systems including control techniques wherein the engine gross output torque required to cause zero drive line torque (i.e., zero flywheel torque) under current vehicle operating conditions is determined and, under various predetermined conditions, the engine is caused to generate such gross output torque. The shift control of the present invention uses torque information from the engine (preferably an electronic engine communicating over an electronic data link), along with vehicle and/or engine acceleration information, to determine various control parameters.
2. Description of the Prior Art
Fully automatic and semi-automatic vehicular mechanical transmission systems and fully or partially automated shift implementation systems utilizing electronic control units, usually microprocessor-based controllers, are known in the prior art. Examples of such automated mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,361,060; 4,425,620; 4,595,986; 4,631,679; 4,648,290; 4,722,248; 5,038,627; 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; 5,089,965; 5,133,229; 5,172,609; 5,231,582; 5,272,939; 5,335,566; 5,435,212; 5,508,916 and 5,509,867, the disclosures of which are incorporated herein by reference.
In accordance with an improved vehicular transmission control, an at least partially automated vehicular mechanical transmission system which accurately determined a value indicative of engine flywheel torque under current vehicle operating conditions was provided. That control is particularly useful for vehicular automated mechanical transmission systems communicating with an electronically controlled internal combustion engine by means of a data link of the type conforming to an industry-established protocol similar to SAE J1922, SAE J1939 or ISO 11898.
In a preferred embodiment of the improved control, the foregoing was accomplished in a vehicular automated mechanical transmission system control by utilizing the relationship that:TEG=TFW+TBEF+TACCES+TACCELwhere:                TEG=gross engine torque;        TFW=engine flywheel torque;        TBEF=base engine friction torque (includes the torque to overcome engine internal friction and the torque to rotate the engine manufacturer-installed accessories (i.e., water pump, oil pump, etc.));        TACCES=accessory torque (torque to operate vehicle accessories, such as air-conditionings, fans, lights, etc.); and        TACCEL=torque to accelerate engine, calculated from engine acceleration or deceleration and momentof inertia (I) of engine.        
Instantaneous values representative of gross engine torque (TEG) and base engine friction torque (TBEF) are available on the data link. TACCEL is determined from sensed engine acceleration (which may be negative) and a calibrated moment of inertia (I) of the engine. Accessory torque (TACCES) is a constantly determined value which, Applicant has determined, may be taken as net engine torque (i.e., TEG-TBEF) if the vehicle is idling with the transmission in neutral and is related to engine deceleration rate in a known, substantially linear manner when the vehicle is in motion.
An adaptive control system/method for an at least partially automated vehicular mechanical transmission system which continuously updates the value of a control parameter (TFW) indicative of flywheel torque may be seen by reference to aforementioned U.S. Pat. No. 5,509,867.